Field of the Invention
The present invention relates to a zoom lens and an image pickup apparatus including the same, which are suitable for an image pickup optical system used in an image pickup apparatus, for example, a digital camera, a video camera, a TV camera, a monitoring camera, or a silver-halide film camera.
Description of the Related Art
In recent years, as image pickup optical systems that are used in image pickup apparatus each using a solid-state image pickup element, there is a demand for zoom lenses that are small as a whole and have a high zoom ratio and high optical characteristics over an entire zoom range thereof. Further, such image pickup optical systems are demanded to be zoom lenses having an image stabilization mechanism configured to correct an image blur. In general, an image stabilizing unit is configured to move during image blur correction in a direction perpendicular to an optical axis. When the image stabilizing unit is moved in the direction perpendicular to the optical axis, decentering aberration is generated.
There has hitherto been known a zoom lens in which a plurality of image stabilizing units are configured to move in a direction perpendicular to an optical axis in order to reduce decentering aberration that is generated during image blur correction. In Japanese Patent Application Laid-Open No. 2001-249276, there is disclosed a five-unit zoom lens including, in order from an object side to an image side, a first lens unit to a fifth lens unit having positive, negative, positive, negative, and positive refractive powers, respectively, in which the second lens unit and the fourth lens unit are configured to move during image blur correction in a direction perpendicular to an optical axis.
In Japanese Patent Application Laid-Open No. H07-27978, there is disclosed a four-unit zoom lens including, in order from an object side to an image side, a first lens unit to a fourth lens unit having positive, negative, negative, and positive refractive powers, respectively, in which the third lens unit and the fourth lens unit are configured to move during image blur correction in a direction perpendicular to an optical axis. In Japanese Patent Application Laid-Open No. 2012-141598, there is disclosed a four-unit zoom lens including, in order from an object side to an image side, a first lens unit to a fourth lens unit having positive, negative, positive, and negative refractive powers, respectively, in which a plurality of image stabilizing units defined in the fourth lens unit are configured to move in a direction perpendicular to an optical axis.
There is a demand for a zoom lens having an image stabilization function in which, during image blur correction, the amount of decentering aberration is small, and satisfactory optical characteristics may be maintained.
In general, in order to provide a large image stabilization angle, it is necessary to greatly decenter an image stabilizing unit (increase the decentering amount thereof), or to increase image stabilization sensitivity. When the decentering amount of the image stabilizing unit is increased, in general, decentering aberration is greatly generated as well to reduce optical characteristics. Further, in order to enhance the image stabilization sensitivity of the image stabilizing unit, it is generally necessary to increase a refractive power of the image stabilizing unit. However, with the increased refractive power, decentering aberration is greatly generated during decentering to reduce the optical characteristics.
In order to reduce aberration variations during image blur correction while ensuring a large image stabilization angle, it is important to appropriately set the lens configuration of a zoom lens, the number of image stabilizing units for image blur correction, the lens configuration of each image stabilizing unit, and the like. If an image stabilizing unit configured to move for image blur correction is not appropriately selected or the lens configuration of an image stabilizing unit is not appropriately determined, a large image stabilization angle is not obtained, that is, image blur correction is not sufficiently performed. In addition, the amount of decentering aberration that is generated during image stabilization is increased, leading to difficulty in maintaining high optical characteristics during image stabilization.